Forest structure of selected vegetation types of Arabuko-Sokoke forest and natural regeneration of Brachylaena huillensis

Abstract

Arabuko Sokoke forest is located on the Kenyan coast and is the only remaining single block of the previously expansive coastal tropical forest in eastern Africa. The forest has high endemicity of both floral and faunal species. Brachylaena huillensis is one of the most commercially valuable species in the forest, being used in the wood carving industry. Thus, it has been over-exploited over the years. A study was therefore conducted to describe the present ecological status of B. huillensis including its regeneration dynamics as influenced by forest structure. The species is found within the Cynometra thicket and the mixed forest, two of the three broad forest types that constitute Arabuko Sokoke Forest. The forest structure of Cynometra thicket and mixed forest shows a history of disturbance, particularly with regards to Brachylaena huillensis. B. huillensis is disproportionately well represented in the lower size classes of trees but very few reproductive stage mature trees. Natural regeneration is also irregular with higher population of bigger seedlings than young ones. Latent regeneration of B. huillensis is lower than is necessary to perpetuate the species into the mature stages in the long-term. Understanding the reproductive cycles of the species and establishment of the ideal sex ratio in the forest is therefore suggested. In general protection of mature reproductive trees should be explored as an urgent management option.